1. Field of the Invention
This invention relates in general to the field of cellular communications, and more particularly to a method and apparatus for improving communications over cellular networks by maximizing the use of common hardware and software in a mobile station that provides for multiple cellular subscriptions.
2. Description of the Related Art
The cell phone industry is undergoing exponential growth, not only in this country, but all over the world. In fact, it is well known that the over twenty percent of the adult population in the United States do not even have a traditional landline telephone. In addition to those who do not own a conventional telephone, nearly ninety percent of the adult population owns a wireless phone.
Meanwhile the usage of cell phones is increasing as well over the use of traditional landline telephone coverage. In fact, one in seven adults now uses only cell phones. Whereas in the past cell phones were used when a landline was not available or under emergency conditions, lower carrier rates, affordability of family packages, and free mobile-to-mobile or friend-to-friend promotions have fostered in significant increases in usage. It is not uncommon today to walk into any public forum or facility and notice a majority of the people there talking on their cell phones.
Beyond our borders, cell phone use is often times more prevalent than it is in this country due to the fact that wireless infrastructures are more easily deployed that traditional landline infrastructure. As one skilled in the art will appreciate, it is not uncommon in many parts of the world, and more rural areas of the United States, to note exclusive use of cell phones.
Many cellular providers offer subscriptions that include roaming for a fixed additional monthly fee. That is, when calls are placed or received in a region that is covered by a different cellular service provider, the per-minute roaming costs associated with the call are not passed on to the user. These plans that preclude per-minute roaming charges are often referred to as “national” or “nationwide” plans.
However, in many parts of this country, as in other parts or the world, per-minute roaming charges are passed on to the user. And under many imaginable practical scenarios where cell phone service may be the only option, a user may have to subscribe to more than one cellular service just to keep the costs down. Consider a commuter who lives in one city served by one cellular company and who commutes to work in another city that is served by another cellular company. In the absence of a non-roaming plan, the user is forced to carry two cell phones, or at best to swap out user modules in a single cell phone that is compatible with both cellular networks. This is undesirable. It is rather desirable to carry one phone that is capable of concurrently monitoring for and placing calls associated with, say, both of his/her subscriptions, and a particular subscription is employed to make calls depending upon the user's location.
But to accommodate more than one subscription, in addition to providing for storage of user identification information unique to each subscription service, the mobile station itself must be able to monitor control channels, paging channels, and assigned frequencies, among other functions, for both, or more than two subscription services. Yet, as one skilled in the art will appreciate, to perform two tasks at the same time may require duplicate hardware or software resources within the phone. And this is undesirable.
Therefore, what is needed is an apparatus and method where a single mobile phone can monitor and place calls associated with more than one cellular subscription service that maximized the use of common hardware and software within the mobile phone.
In addition, what is needed is a technique for mapping control channels, paging channels, and other parameters needed for a cell phone to communicate over a cellular network, where the mapping is performed in a manner that minimizes the use of separate resources within a cell phone while still maintaining acceptable quality of service.